.\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
.\"
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.TH FSEEKO 3  2021-03-22 "" "Linux Programmer's Manual"
.SH NAME
fseeko, ftello \- seek to or report file position
.SH SYNOPSIS
.nf
.B #include <stdio.h>
.PP
.BI "int fseeko(FILE *" stream ", off_t " offset ", int " whence );
.BI "off_t ftello(FILE *" stream );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR fseeko (),
.BR ftello ():
.nf
    _FILE_OFFSET_BITS == 64 || _POSIX_C_SOURCE >= 200112L
.fi
.SH DESCRIPTION
The
.BR fseeko ()
and
.BR ftello ()
functions are identical to
.BR fseek (3)
and
.BR ftell (3)
(see
.BR fseek (3)),
respectively, except that the
.I offset
argument of
.BR fseeko ()
and the return value of
.BR ftello ()
is of type
.I off_t
instead of
.IR long .
.PP
On some architectures, both
.IR off_t
and
.I long
are 32-bit types, but defining
.BR _FILE_OFFSET_BITS
with the value 64 (before including
.I any
header files)
will turn
.I off_t
into a 64-bit type.
.SH RETURN VALUE
On successful completion,
.BR fseeko ()
returns 0, while
.BR ftello ()
returns the current offset.
Otherwise, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
See the ERRORS in
.BR fseek (3).
.SH VERSIONS
These functions are available under glibc since version 2.1.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR fseeko (),
.BR ftello ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SUSv2.
.SH NOTES
The declarations of these functions can also be obtained by defining
the obsolete
.B _LARGEFILE_SOURCE
feature test macro.
.SH SEE ALSO
.BR fseek (3)
.SH COLOPHON
This page is part of release 5.13 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
